1. Field of the Invention
The present invention pertains to cartons, and in particular to cartons constructed from paper product such as paperboard and cardboard.
2. Description of the Related Art
It is desirable, in many applications, to ship cartons in a "knocked-down" condition, preferably in the form of flat blanks stacked in palletized loads. When shipped to a user, the palletized loads are easily stored until needed. Thereafter, the carton blanks can be removed and erected as required.
In general, it is desirable that the carton blank be erected without requiring the use of adhesives or fasteners such as staples and the like, and users prefer carton blank designs where only a few simple folding operations are needed to fully erect a carton. From a load-carrying standpoint, the carton bottom construction is most critical and considerable attention has been paid over the years this aspect of foldable carton constructions.
It is known, for example, to provide a carton bottom construction with interlocking bottom flaps, where a corner or edge of one bottom flap is inserted in a minimally sized slit formed in an adjoining carton flap. Examples of such constructions are found in U.S. Letters Pat. Nos. 292,683; 490,167; 980,931; 1,997,660; 2,339,224; 2,990,993; and 4,367,840. At times, it is difficult to insert a carton flap into a slit in an adjoining carton panel, and attempts have been made to provide enlarged slits for receiving the corners or edges of an adjoining bottom closure flap. Examples of such constructions are given in U.S. Letters Pat. Nos. 2,361,603; 3,074,613; 3,178,096; 4,279,377; 4,279,379; 4,291,827; 4,614,298; and 4,702,408.
Enlarging the slots on carton bottom panels made it easier to insert adjacent flaps therein. However, concerns were raised that the retention ability of the resulting carton bottom constructions would be compromised. Attempts have been made to improve the locking retention of carton bottom constructions having enlarged slots for receiving the edges or corners of adjacent carton bottom panels. For example, U.S. Letters Pat. No. 4,650,112 provided enlarged L-shaped slots on the major-sized carton bottom panels The minor flaps of the carton bottom have a central, rectangular cutout forming locking legs at the corners of the minor flap. The legs are inserted into the L-shaped slot and engage one side of the slot, to provide flap retention. A similar flap retention is provided in U.S. Letters Pat. No. 4,821,949 and Austria Pat. No. 218,420.
Despite such developments in carton bottom constructions, improvements are constantly being sought. For example, U.S. Pat. Nos. 4,650,111 and 4,821,949 provided score lines on the carton flap carrying the locking legs to facilitate insertion of the legs in a locking slot or a slit formed in an adjacent carton bottom panel. The legs provided for locking are disposed at corners of a carton bottom flap, and are separated by an intervening generally rectangular cutout portion. The legs located at the corners of the carton flap are prone to bending, resulting in a reduced area of contact between the locking legs and the carton flaps receiving those legs. It is desired to make such legs stronger and to more efficiently use the material in that portion of the carton blank allocated to the locking legs.
It is desirable to form the locking portions of a carton bottom panel in an economical manner, so as to maximize the usefulness of the carton material employed in locking the carton bottom. For example, U.S. Pat. No. 4,702,408 provides locking flaps with pairs of spaced apart generally truncated V-shaped notches, defining locking corners. The locking portions are received in rectangular openings formed in adjacent carton flaps, oriented along diagonals of the carton bottom. The locking portions of the mating flaps are generally arranged at angles to one another, with a reduced area of contact, reducing the efficient use of the material used in the interlocking member. The same problems are experienced in the collapsible box of U.S. Letters Pat. No. 2,361,603 which utilizes generally truncated triangular notches in one locking panel, receivable in diagonal slits expanded to form an arcuate edge. I is desirable to improve the design of carton locking members so as to more efficiently use the material of the interlocking components.
These and other objects according to the present invention, which will become apparent from studying the appended description and drawings, are provided in a carton apparatus comprising a tubular body with a pair of opposed sidewalls and a pair of opposed endwalls, and at least one closure extending from the sidewalls and endwalls so as to form at least a partially enclosed interior therewith. The closure comprises:
end panels joined to the endwalls with a hinge line so as to be foldable into a common plane; PA0 the end panels each having a discontinuous free edge remote from the hinge line and a pair of free corners remote from the hinge line and extending from the free edge, the end panels further comprising a fold line between the free edge and the hinge line so as to divide the end panels into two parts to allow the part carrying the free edge to be swung out of the plane of the other end panel part; PA0 the end panels including a recessed edge located between the free corners of the end panels and extending adjacent the end panel free edge, the recessed edge including a pair of spaced, generally U-shaped locking edge portions extending from the end panel free edge and a generally arcuate intermediate portion disposed therebetween, with the U-shaped locking edge portions defining a pair of opposed, generally arcuate panel-receiving slits; PA0 the U-shaped locking edge portions cooperating with the end panel free edge to define a pair of opposed locking ears extending toward one another, one on either side of the intermediate arcuate edge portion; PA0 side panels joined to the sidewalls with a hinge line so as to be foldable toward the common plane; PA0 a pair of locking recesses formed in each side panel, each recess including an arcuate edge portion having an exterior end adjacent PA0 the sidewall hinge line and an interior end remote therefrom, and a generally truncated V-shaped edge portion extending generally between the interior and exterior ends of said arcuate recess edge, with a part of the truncated V-shaped edge immediately adjacent the interior end comprising a locking edge which is matingly engageable with the U-shaped locking edge portions of the end panels, and with the truncated V-shaped edge portions of a side panel extending toward one another with adjacent converging ends; and PA0 the side panels and end panels foldable toward a common plane, with the locking tabs of the end panel deflecting the hinge tabs into the interior of the carton to form recesses in the side panels into which the locking tabs are inserted so that the locking edge of the tab engages the locking edge of the side panels.